Ubuntu – Can apt actions delete/modify files inside exiting user home

apthome-directorypackaging

I somehow always assumed that when I run a command like apt-get install, remove, purge then at most apt might add configuration dot-files files to my existing local home (not even sure about that), but NEVER modify or delete any files there (without backing up).

Is there any such restriction or at least guideline?

Best Answer

There are two issues:

Debian policy dictates how home directories are managed and properly packaged .deb should not modify anything in users home directories.

9.2.3. Non-existent home directories The canonical non-existent home directory is /nonexistent. Users who should not have a home directory should have their home directory set to this value.

The Debian autobuilders set HOME to /nonexistent so that packages which try to write to a home directory will fail to build.

10.7.5. User configuration files (“dotfiles”) The files in /etc/skel will automatically be copied into new user accounts by adduser. No other program should reference the files in /etc/skel.

Therefore, if a program needs a dotfile to exist in advance in $HOME to work sensibly, that dotfile should be installed in /etc/skel and treated as a configuration file.

However, programs that require dotfiles in order to operate sensibly are a bad thing, unless they do create the dotfiles themselves automatically.

Furthermore, programs should be configured by the Debian default installation to behave as closely to the upstream default behavior as possible.

Therefore, if a program in a Debian package needs to be configured in some way in order to operate sensibly, that should be done using a site-wide configuration file placed in /etc. Only if the program doesn’t support a site-wide default configuration and the package maintainer doesn’t have time to add it may a default per-user file be placed in /etc/skel.

/etc/skel should be as empty as we can make it. This is particularly true because there is no easy (or necessarily desirable) mechanism for ensuring that the appropriate dotfiles are copied into the accounts of existing users when a package is installed.

See : https://www.debian.org/doc/debian-policy/ for details

HOWEVER .....

Installing .deb requires root authorization and packages can run pre and post install scripts that modify files in home directories in violation of debian policy or people who package .deb may choose to ignore debian policy.

So it is possible for .deb to violate debian policy and alter files in user home directories.

This is one of many considerations or reasons you should be very careful when installing .deb from outside the Ubuntu repositories.

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Ubuntu – How to detect and delete all lost configuration folders

I can't think of a quick fix short of going through deleting what you know isn't installed and manually Googling what you can't identify. It's a horrible problem that I've just opted for the Etch-a-Sketch method and either deleted my whole profile or have deleted large chunks of it (.config, .gnome-2, etc)

The only long term solution I could think of doing this is setting up an online database of:

Packages
What configuration paths they use

You'd store that information in a simple JSON "database", perhaps gzip it and store it somewhere online.

You'd then have a tool that downloaded this global list and scanned the paths, looking for corresponding paths in the user's home. Where there are matches, you check the package list to see if that package is still installed. If it's not, it goes on a death-list.

After that scan, the user gets a list of available clean-up operations (with detail on what package the program thinks it is) and it given the option to nuke whatever they like.

In a perfect world, we'd have this integrated right into the packaging system (and have apt-get clean-my-home), but I think that's a pipe dream. Maintainers would have to do a ton of work on top of requiring reengineering the package database formats (which are shakey enough already).

As getting this written into the fabric of each package is unappealing, there also needs to be some sort of interface for normal people to suggest paths for packages. (As it's my dayjob) I'd probably suggest a quick and dirty web-app where people can make their suggestions and MOTUs, Ubuntu members, etc can moderate the flow to make sure people aren't suggesting potentially dangerous searches.

As it is, it's going to require a whole load of manpower to get the however-many thousand apps that write home-files.

This is an interesting problem. This might give me a good excuse to play with Quickly's cli template (Quickly because I'm a Pythonista and also because packaging scares me).

Ubuntu – Reinstalling Ubuntu without formatting /home, as well as without any old config files

I've done this quite often now - almost every time I did upgrade my system or (especially) if I switched to another distro. I normally log out, go to a console and log in as root directly (or depending on system configuration, as another user and switch to root), cd to /home folder and simply change my user's home folder name e.g. to "myUserName.bak". e.g.:

sudo mv /home/myUserName /home/myUserName.bak

After installation I can safely move all data needed to the newly created home folder for my user. (That's also a good point for thinking whether you e.g. really need that folder of big files you never touched the last 2 years ;) )

edit as suggested by comments: before you can access the files and folders from your renamed home folder you have to

sudo chown -R newUser.newUsersGroup /home/myUserName.bak

Best Answer

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